Stuff to update the learning guide with

[evaherrada]

Feather boards and many other circuitpython boards will round to two decimal places like this:

>>> float('1234.5678')
1234.57

This isn't ideal for gps data and other applications that require high amounts of accuracy as this lowers the accuracy from 0.1m to 11m.

This can be fixed by using string formatting when the gps data is outputted.

An implementation of this can be found in examples/gps_simpletest.py

import time
import board
import busio

import adafruit_gps

RX = board.RX
TX = board.TX

uart = busio.UART(TX, RX, baudrate=9600, timeout=30)

gps = adafruit_gps.GPS(uart, debug=False)

gps.send_command(b'PMTK314,0,1,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0')

gps.send_command(b'PMTK220,1000')

last_print = time.monotonic()
while True:

    gps.update()

    current = time.monotonic()
    if current - last_print >= 1.0:
        last_print = current
        if not gps.has_fix:
            print('Waiting for fix...')
            continue
        print('=' * 40)  # Print a separator line.
        print('Latitude: {0:.6f} degrees'.format(gps.latitude))
        print('Longitude: {0:.6f} degrees'.format(gps.longitude))

These two lines are the lines that actually solve the issue:

print('Latitude: {0:.6f} degrees'.format(gps.latitude))
print('Longitude: {0:.6f} degrees'.format(gps.longitude))

Extra stuff: This Image explains what the is in the GNSS list quite well.

Click here to learn about decimal degrees, which is the format that the GPS library outputs lat and long data

Click here to learn about geographic coordinate conversion.

[evaherrada]

@kattni

[evaherrada]

About NMEA Data

This GPS module uses the NMEA 0183 protocol.

This data is formatted by the GPS in one of two ways.

The first of these is GGA. GGA has more or less everything you need.

Here's an explanation of GGA:

                                                        11
           1         2       3 4        5 6 7  8   9  10 |  12 13  14   15
           |         |       | |        | | |  |   |   | |   | |   |    |
    $--GGA,hhmmss.ss,llll.ll,a,yyyyy.yy,a,x,xx,x.x,x.x,M,x.x,M,x.x,xxxx*hh

1. Time (UTC)
2. Latitude
3. N or S (North or South)
4. Longitude
5. E or W (East or West)
6. GPS Quality Indicator,
   • 0 - fix not available,
   • 1 - GPS fix,
   • 2 - Differential GPS fix
7. Number of satellites in view, 00 - 12
8. Horizontal Dilution of precision
9. Antenna Altitude above/below mean-sea-level (geoid)
10. Units of antenna altitude, meters
11. Geoidal separation, the difference between the WGS-84 earth ellipsoid and mean-sea-level (geoid), "-" means mean-sea-level below ellipsoid
12. Units of geoidal separation, meters
13. Age of differential GPS data, time in seconds since last SC104 type 1 or 9 update, null field when DGPS is not used
14. Differential reference station ID, 0000-1023
15. Checksum

The second of these is RMC. RMC is Recommended Minimum Navigation Information.

Here's an explanation of RMC:

                                                        11
       1         2       3 4        5 6 7  8   9  10 |  12 13  14   15
       |         |       | |        | | |  |   |   | |   | |   |    |
$--RMC,hhmmss.ss,llll.ll,a,yyyyy.yy,a,x,xx,x.x,x.x,M,x.x,M,x.x,xxxx*hh

1. Time (UTC)
2. Status, V = Navigation receiver warning
3. Latitude
4. N or S
5. Longitude
6. E or W
7. Speed over ground, knots
8. Track made good, degrees true
9. Date, ddmmyy
10. Magnetic Variation, degrees
11. E or W
12. Checksum

Info about NMEA taken from here